The Effect Of Leg Mass On Cycling Efficiency

PURPOSE: With several high-cadence cyclists repeatedly winning the Tour de France over that last decade, there has been renewed interest in the affect of pedaling cadence on cycling efficiency. Decades ago, Jim Hagberg and colleagues reported that increasing pedaling frequency during unloaded cycling caused an increase in VO2 (decrease in efficiency). Thus, the increased work of moving the legs may explain much of the decline commonly reported with increasing pedal frequency. The purpose of this study was to directly examine the relationship between leg mass, pedal frequency, and cycling efficiency. METHODS: Within a randomized crossover study design 16 biological females and 13 biological males (mean age: 22 yr.; mean BMI:23.5 kg/m2) were randomly assigned to either a pedal cadence of 60 rpm at normal leg weight (60U), 90 rpm at normal leg weight (90U), or 60 rpm with 50% increase in leg mass (60W). Leg mass was measured by DEXA. Participants cycled on either an electronically (n=20) or manually braked (n=9) cycle ergometer at an external power output of 70 watts for 7 minutes. Oxygen consumption was continuously measured using indirect colorimetry. VO2 was averaged over the last 3 minutes. Heart rate was continuously monitored and returned to baseline before the participants crossed over to the next condition. RESULTS: Increasing pedal frequency by 50% from 60 rpm to 90 rpm resulted in an increase in VO2 of 4.5+1.5ml/kg/min. Increasing leg mass by 50% also resulted in a similar increase in VO2 of 3.8+1.7 ml/kg/min. A t-test for repeated measures revealed no statistical difference between comparisons (p=0.40; Cohen's d=0.43). CONCLUSION: These data indicate the decrease in cycling efficiency commonly reported with increasing pedaling cadence in almost entirely explained by the additional biomechanical work of moving one’s leg mass.